In many of today's processing systems, such as personal computer (PC) systems, there exist universal serial bus (USB) ports for connecting various USB devices. Some of these USB devices are frequently used by PC users. For example, these USB devices may be printers, compact disk read-only-memory (CD-ROM) drives, CD-ROM Writer (CDRW) drives, digital versatile disk (DVD) drives, cameras, pointing devices (e.g., computer mouse), keyboards, joy-sticks, hard-drives, speakers, etc. Some of these devices use more of the available USB bandwidth than others. For example, a USB CDRW is a high bandwidth device, while human interface devices (HID), such as computer mice, keyboards and joysticks, are low bandwidth devices.
Within a USB cable there are typically four shielded wires. Two of the wires may provide power (+5 volts (red) and ground (brown)) and a twisted pair (blue and yellow) for data.
At either end of a USB cable there is a standard sized connector. These connectors each has a different profile designated “A” connectors and “B” connectors. More recently, mini versions of these connectors are appearing to accommodate smaller devices. “A” connectors head “upstream” toward the computer. On the other end, “B” connectors head “downstream” and connect to individual devices. This way, it is almost fool proof to make a wrong connection.
The USB standard allows for low power devices (e.g., mice, memory sticks, keyboards, etc.) to draw their power from their USB connection. Larger devices requiring more power, such as scanners or printers, typically have their own dedicated power supply.
FIG. 1 shows a typical USB “A” male connector 10. The cable 12, comprises the above mentioned four wires and connects to a plastic housing 14. Each of the four wires electrically connects within the housing 14 to one of four contact terminals or pins 16 mounted on the top side of an insulative base 18. The insulative base 18 is wrapped in a metal shield 19. Openings 20 in the metal shield may be provided to lock the connector in place when plugged into a corresponding female connector.
FIG. 2 shows a more detailed view of the insulative base 18. As shown, conductive fasteners 21, 22, 23, and 24 are provided at one end to connect to each of the four wires in the cable 12. The outer two fasteners 21 and 22, are for power and the inner two connectors 23 and 24 are for data. On a top side of the insulative base 18 are four pins 31, 32, 33, and 34, corresponding to the contacts 21, 22, 23, and 24, respectively. The pins 31-34 within the male connector 10 electrically engage to mating pins within the female connector when plugged in.
Different standards of USB technology have different bandwidths. For instance, Universal Serial Bus Specification, revision 1.1, Sep. 23, 1998 (USB 1.1) devices are capable of operating at 12 Mbits/second (Mbps). Universal Serial Bus Specification, revision 2.0, Apr. 27, 2000 (USB 2.0; also known as high-speed USB) devices are capable of operating at 480 Mbps. However, as technology progresses engineers are constantly striving to increase operating speeds.